So, I am going through my Hayne's manual and it shows me the location of the fuel filter. I have a 3.0 with fuel injection. Since I just got the truck and don't know the condition, I replace it. No problem... until I found another fuel filter that leads directly to the fuel rails. The filters are directional, showing in and out arrows, but the one on the driver's side, just under the cab had the arrow (labeled IN) pointing toward the fuel tank.
Question... do the high pressure filters have a check valve system to help maintain fuel pressure? Could this filter (that looks like it is installed backward) be the problem I am having with loosing fuel pressure when the engine is off?
I thought it had only one filter for my system...
Any help?

 

There should be only one stock fuel filter and it is in the frame rail under drivers seat area.

IN would be correct for the fuel line coming from the fuel tank, fuel is flowing IN to the filter and OUT to the engine.

No, on a 1991 there is a check valve inside the fuel pump, it isn't a separate piece.

And there is a Fuel Pressure Regulator(FPR) on the fuel rail/engine that is connected to the fuel Return line that runs back to the fuel tank, so there are 2 fuel lines.

The FPR and fuel pump's check valve are what hold fuel pressure in the system when engine and fuel pump are off.

Could that second fuel filter be on the return line?
Not sure why it would be there.

Could you be mistaking the FPR(round cylinder) with return fuel line attached, as a filter?
FPR also has a vacuum hose attached.

FPR is a spring loaded valve and should hold fuel pressure up to 40psi then it will start to open and send extra fuel and pressure back to the fuel tank.
You can carefully pinch off Return fuel line, i.e. vise grips but don't crush it, and then cycle key on and off 2 or 3 times(fuel pump runs for 2 seconds each time key is turned on).
Then see if fuel pressure holds.
If it does then replace FPR, it is leaking
If fuel pressure still drops then Check Valve is the problem, so have to replace whole fuel pump.

There are slight differences in designs but this is a picture of an FPR: http://www.partsgeek.com/assets/dimage/full/1200403.jpg
1 vacuum hose connection
1 connection to Fuel rail
1 connection for return fuel line

 

I was wrong about the two filters. My mind is going. I bought the FPR you suggested but I haven't installed it yet. It's hard to get to the screws that holds it to the bracket. It would have been an easy thing to have those screws on top of the regulator. Access isn't always first priority when they design these things.
If this doesn't solve the pressure drain I will just put up with it. It's manageable. I just turn the key on and let the pump cycle then simply key the starter for about 2 seconds and let the pump cycle again. Do that about three times and it starts like there is no problem.
Thanks for the help